LEP and obesity due to melanocortin 4 receptor deficiency: Such a blunted sympathetic response or sympathetic reserve may promote weight gain and aggravate insulin resistance and subsequent hyperinsulinemia, and thus maintain the vicious circle of weight gain—insulin resistance—sympathetic activation with blunted response—weight gain, etc. Increased leptin secretion by the adipocytes in patients with obesity contributes to vascular and systemic insulin resistance and SNS dysfunction [3, 4].